State and federal health officials are cooperating in a study of Eastern equine encephalitis, a mosquito-transmitted virus that killed two Vermonters last year.

“There’s no specific hypothesis,” said Matthew Thomas, an epidemiologist with the infectious diseases section of the Vermont Department of Health. “Because there’s, honestly, very little known about what the prevalence of the triple-E antibody is in a population. We want to see what it is in Vermont.”

The plan is to draw blood from volunteers, ages 12 and older, who have lived in Brandon, Whiting or Sudbury since at least June 1 of last year. The first recorded EEE deaths in the state were in Sudbury and Brandon last year. There was also a horse death and the virus was suspected in the deaths of a number of emus on one human victim’s farm.

Thomas said researchers hope to get 150 to 200 people at each of three clinics being organized to collect blood.

The first clinic runs 10 a.m. to 7 p.m. April 23 at the Brandon Senior Center on Forest Dale Road. The second is noon to 7 p.m. May 14 at the Sudbury Town Hall. The third is noon to 7 p.m. at the Whiting Town Hall.

Blood specimens will go to the federal Centers for Disease Control for testing and results will come back to Vermont for data analysis. Thomas said he hopes to have preliminary results eight to 12 months after the final clinic.

Researchers will also ask participants about activities that might increase risk of exposure, seeing if particular activities correlate to a greater level of infection.

“I think, typically, when people present with triple-E illness, that is the first time we know they’re infected,” he said.

However, participants will not be told the results of their tests. Thomas said the test being used is not approved for clinical use and may only be used for the study.

He said there is also a fear that a negative result might make a participant think he or she is immune. Finally, there is no course of treatment for someone who is infected but does not show symptoms, according to Thomas.

Thomas said those worried they might be infected can be tested by their doctors.

“The primary purpose of what we’re doing is to find out what the current burden is right now,” he said.

The state already monitors the mosquito population.

“The only thing that was extremely alarming for me is last year, at one site where I’ve trapped for a few years, there was an exceptionally large vector for Eastern equine encephalitis,” state entomologist Alan Graham said. “It was in Whiting.”

EEE is found primarily in one species of mosquito — culiseta melanura. Graham said other species are known to carry it, but that there was discussion on how important they are in transmission of the disease.

Culiseta melanura is particularly important, Graham said, because EEE is found primarily in birds and that species feeds heavily from birds. He said the disease appears primarily in July and August.

“It disappears in October and nobody knows where it goes until it shows up again in July,” he said.

Mosquitoes carry a number of different diseases, Graham said, but most do not affect humans.

Larvacide has proven effective in controlling the populations of mosquitoes that would otherwise appear in “enormous” numbers following summer rainstorms, he said. Last year, because of the public health emergency, was the first time the state used a pesticide aimed at adult mosquitoes.

“That appeared to be very effective, but it was late in the season,” he said, adding that it would have been even more effective earlier in the year.

Graham said he expects more such mosquito treatments this year due to last year’s deaths.